/Engine/Plugins/Runtime/MeshModelingToolset/Source/MeshModelingTools/Public/EditMeshPolygonsTool.h
Collapse the selected edges, deleting the attached triangles and merging its two vertices into one
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(CallInEditor, Category=EdgeEdits, Meta=(DisplayName="Collapse", DisplayPriority=1)) void Collapse()